Ten years after the Sept. 11, 2001, terrorist attacks on the World Trade Center, roughly half of the eight-acre memorial plaza designed to take its place is a fenced-off hole in the ground. The underground memorial museum and its above-ground steel-and-glass pavilion are still under internal construction. There is less still to the commercial portion of the 16-acre site, where half-clad skyscrapers stand among ditches awaiting foundations to be poured. On the 10th anniversary of the attacks, the World Trade Center is very much a work in progress.

The memorial and its plaza were designed for three functions: to give Lower Manhattan some much-needed public space, to commemorate the city’s loss of the Twin Towers and the people who perished in them, and to serve as a breathtaking icon of renewal. The memorial and a section of the plaza will open for the 10th anniversary of the attacks, with the museum, pavilion and remainder of the plaza set to open next year.

Yet for all the time it will take to re-open the World Trade Center, it may take much longer for New Yorkers to decide what to make of it. How the memorial and plaza will fit into Manhattan will depend as much on what the city brings to it as what it brings to the city.

Case in point: Before the stainless steel cladding was added to the memorial pavilion, construction workers on the site mistook the pavilion’s shaded, striped glass for a U.S. flag design. “It was like breaking their heart to say no,” says Ann Lewison, project manager for Snøhetta, which designed the pavilion. “It’s interesting to work on a site where people bring their own meaning.”

When the first visitors arrive this fall, there will be other incomplete features that call for interpretation. Over a decade of development, the city has introduced its share of changes and delays to the site—some for prosaic reasons of cost and security, others owing to the sensitive nature of the site and the many stewards overseeing its multiple functions.

One proposal would have used the opportunity to entirely revise the neighborhood: a suggestion to sink part of the West Side Highway, which divides the World Trade Center site from the World Financial Center. The memorial plaza would have then extended to World Financial, connecting it and Battery Park City to the rest of Lower Manhattan. Yet the idea came too soon after Boston’s Big Dig; nearby businesses complained to City Hall about the prospects of sinking tens of billion of dollars and years of construction into moving the highway underground.

Ultimately, a comparatively simple World Trade Center master plan emerged. On the 10th anniversary of the attacks, visitors will be able to go right up to where the Twin Towers stood, read the names of the deceased, and take in the dramatic, flat stone boxes of the buildings’ footprints—now smooth waterfalls. But no decision along the way has been easy.

Designing the Memorial

Few subjects in architecture are more contentious and intensely emotional than the representation of historical memory. Michael Arad, AIA, of Handel Architects, who with landscape architect Peter Walker designed the winning proposal for the 9/11 memorial, says that the presentation of victims’ names required multiple revisions. Every victim’s family has a stake in how their loved one is remembered; by no means do all of their interests align.

Initially, Arad and Walker’s design called for a ramp that would wind down around one of the pools to a series of underground galleries with the names of the lost inscribed on the walls. That plan for the inscriptions had to be scrapped: Enclosed galleries would be difficult to outfit with security features. Egress for large crowds in the case of an emergency presented another concern. Arad agreed to bring the names up to street level. “The galleries were not about having a cool vertical space,” Arad says. “It’s about the experience of seeing the names.”

A proposal to present victims’ names inside the museum was similarly impractical. A queue of visitors entering the museum would build to unmanageable levels if every visitor looking to see the memorial names was led through security detectors.

Bureaucratic obstacles emerged for virtually every approach. After the galleries were eliminated for cost and security reasons, Arad suggested putting the names on a shallow water table at the top of the waterfalls. That raised building code issues: A pool deeper than 18 inches can be considered a swimming pool. Symbolically, the idea also could be seen as showing the names drowning. At the request of the National September 11 Memorial and Museum Foundation, Arad went back to the drawing board.

The next, and semi-final, solution was to carve the names into 5-inch-thick bronze plates that would ring the waterfalls. Illuminated from beneath at night, the plates appear to float above the water table in renderings.

It was an elegant answer—but an incomplete one. The Mayor’s Office for People with Disabilities expressed the concern that the void in the Towers’ footprints would not be visible over the parapet to a person seated in a wheelchair. So why not lower the parapet? Again, the answer was codes: The City Building Code requires it to be at least 42 inches high to prevent anyone from falling into the waterfall. “It was one city agency against another,” Arad recalls.

Arad’s solution was to design the parapet with an empty space underneath it so that a person in a wheelchair could bring his or her legs underneath it. Wheelchair users were now being given an ample vantage point. Serendipitously, the Towers themselves featured corners similar to those that Arad had designed for the parapet. “It enriched the design beautifully,” he says. “The names now wrap around instead of stopping and starting four times.”

Even so, not every question could be answered in such a satisfactory way for all of the stakeholders. The names presented an especially vexing riddle: In what order should they be arranged? Should family members be grouped together or split up? Should first responders be given some special recognition? Ultimately the choice to group victims according to where they were that day prevailed.

“You have to detach from personal investment in any design from the over-arching purpose of the design,” Arad says.